July 2004
Volume 45, Issue 7
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Eye Movements, Strabismus, Amblyopia and Neuro-ophthalmology  |   July 2004
Retinal Nerve Fiber Layer Thickness in Unilateral Amblyopia
Author Affiliations
  • May-Yung Yen
    From the Department of Ophthalmology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan, Republic of China.
  • Ching-Yu Cheng
    From the Department of Ophthalmology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan, Republic of China.
  • An-Guor Wang
    From the Department of Ophthalmology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Investigative Ophthalmology & Visual Science July 2004, Vol.45, 2224-2230. doi:https://doi.org/10.1167/iovs.03-0297
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      May-Yung Yen, Ching-Yu Cheng, An-Guor Wang; Retinal Nerve Fiber Layer Thickness in Unilateral Amblyopia. Invest. Ophthalmol. Vis. Sci. 2004;45(7):2224-2230. https://doi.org/10.1167/iovs.03-0297.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

purpose. To test the hypothesis that eyes with amblyopia may have thicker retina, retinal nerve fiber layer thickness (RNFLT) was investigated in patients with unilateral amblyopia.

methods. Thirty-eight patients with unilateral amblyopia were studied. Among them, 20 patients had amblyopia with strabismus and 18 had refractive amblyopia without strabismus. Nineteen of 38 had anisometropia of 2.0 D or more. In addition, 17 patients with anisometropia of 2.0 D or more but without amblyopia were enrolled as control subjects. RNFLT was measured by optical coherence tomography with scan pattern “Nerve Head 2.0R” (Carl Zeiss Meditec, Dublin, CA). Average RNFLT was multiplied with their corresponding scan circumferences to estimate the integral values of the total RNFL area (RNFLTestimated integrals).

results. In all 38 patients with unilateral amblyopia, the difference in RNFLT and in RNFLTestimated integrals between the amblyopic eyes and the normal fellow eyes were statistically significant. Multivariate regression analysis with adjustment for axial length, spherical equivalence, age, and sex indicated significant differences as well. In the group of strabismic amblyopia, the difference in RNFLT and in RNFLTestimated integrals between the amblyopic eyes and the normal fellow eyes did not reach statistical significance. However, in the group of refractive amblyopia, the difference in RNFLT and in RNFLTestimated integrals between the amblyopia eyes and the normal fellow eyes both had a statistical significance. In the 19 patients with anisometropic amblyopia, the difference in RNFLT and in RNFLTestimated integrals between the amblyopic eyes and the normal fellow eyes were statistically significant. In the control group of 17 patients with nonamblyopic anisometropia, the difference in RNFLT and in RNFLTestimated integrals between both eyes did not reach statistical significance.

conclusions. RNFLT may be affected by refractive amblyopia, but further histopathologic confirmation is needed.

Amblyopia is considered to be a developmental disorder of spatial vision that is associated with the presence of strabismus, anisometropia, or form deprivation early in life. 1 If the same disorders occur later in life, amblyopia does not develop. 
The amblyopic process may have an effect on various levels of the visual pathway. Shrinkage of cells in the lateral geniculate nucleus that receive input from the amblyopic eye 2 3 4 5 6 7 and a shift in the dominance pattern in the visual cortex 8 9 10 11 12 have been reported. Retinal involvement accompanying amblyopia is controversial. 13 14 15 16 17  
During fetal development, there is a rapid decline in cell density in the retinal ganglion cell layer toward the end of gestation. In humans, the total population of cells in the ganglion cell layer is highest (2.2–2.5 million cells) between approximately weeks 18 and 30 of gestation. After this, the cell population declines rapidly to 1.5 to 1.7 million cells. 18 The number of axons in the human optic nerve also decreases during gestation. 19 At 16 to 17 weeks of gestation, the estimated number of axons was 3.7 million. The number of axons in the human adult optic nerve is 1.1 million. In rat retina, the number of retinal ganglion cells projecting to the central visual nuclei is reduced by at least 35%, and the process ceases by 2 weeks postnatally. 20 If amblyopia affects the process of postnatal reduction of ganglion cells, RNFL thickness may be thicker than that in the normal eye. It was our plan to investigate retinal nerve fiber layer thickness (RNFLT) in amblyopic eyes to determine whether it is thicker. 
Several techniques to evaluate the RNFLT, such as red-free ophthalmoscopy, scanning laser polarimetry (SLP) and optical coherence tomography (OCT) have been described. SLP estimates RNFLT based on the retardation of the laser beam caused by the birefringence of the RNFL. Because the cornea is also birefringent, erroneous RNFLT assessment can be made without proper anterior segment compensation. 21 22 23 OCT is a noninvasive, noncontact technique that measures RNFLT. 24 25 The RNFLT measured by OCT corresponds to the RNFLT measured histologically. 24 Because OCT is based on near-infrared interferometry, the thickness measurement is not affected by refractive status or axial length of the eye, nor by light changes in nuclear sclerotic cataract density. 26 RNFLT remains unchanged after laser-assisted in situ keratomileusis (LASIK). 27 Posterior subcapsular and cortical cataracts, heavy nuclear cataracts, secondary cataracts, loss of vitreous body transparency, and silicone oil in the vitreous chamber, however, reduce the ability to perform OCT. 26 28 Excluding these conditions, OCT is a reliable imaging technology. The purpose of our investigation was to use OCT to measure RNFLT in patients with unilateral amblyopia, to see whether the RNFL is thicker in the amblyopic eye. 
Materials and Methods
Subjects
Approval for this project was obtained from the institutional review board of Taipei Veterans General Hospital. The study was performed according to the tenets of the Declaration of Helsinki for research involving human subjects. Patients with unilateral amblyopia were consecutively enrolled. Clinical examinations included best corrected visual acuity, refraction error, slit lamp examination, extraocular movements, intraocular pressure, fundoscopy, and A-scan for axial length. Patients with organic eye disease, a history or evidence of intraocular surgery, history of cataract, glaucoma, retinal disorders, or laser treatment and children not cooperative enough for OCT examination were excluded. 
A total of 38 patients with unilateral amblyopia were enrolled. Twenty had strabismic amblyopia (Table 1) . The other 18 without strabismus had a diagnosis of refractive amblyopia (Table 2) . Of the 38 patients with unilateral amblyopia, 19 also had anisometropia, including 7 from the group with strabismic amblyopia and 12 from the group with refractive amblyopia (Table 3) . Anisometropia was defined as a difference in spherical equivalence of 2.0 D or more between the two eyes. For the purpose of comparison, in addition, 17 patents with nonamblyopic anisometropia were enrolled as control subjects (Table 4)
OCT Technique
After obtaining informed consent, the pupils were dilated with 1 drop of 1% tropicamide. RNFLT was measured by OCT 30 minutes later. The OCT system used in this study was OCT model 2000 (Carl Zeiss Meditec, Dublin, CA). The software version was 5.1. A peripapillary circular scan with scan pattern “Nerve Head 2.0R” was carefully positioned. The same scan pattern was used in all cases. Internal fixation was chosen unless the amblyopia was too deep to follow the fixation target. Average RNFLT detected by the circular scan was measured three times in each eye. Figure 1 showed a single OCT scan. All OCT measurements were performed by one of the authors (C-YC) who was not blind to the diagnosis. In every case, the right eye was always measured first, followed by the left eye. 
Statistical Analysis
The mean of the three RNFLT measurement and RNFLTestimated integrals 29 obtained from each eye were used for statistical analysis. Average RNFLT was multiplied with their corresponding scan circumferences to estimate the integral values of the total RNFL area: RNFLTestimated integrals (μm2) = RNFLTaverage (μm) × scan circumference (μm). Results are presented as mean ± SD. A paired Student’s t-test was used to assess the difference in RNFLT and in RNFLTestimated integrals between amblyopic and normal eyes in the patients with unilateral amblyopia and between both eyes of the patients with nonamblyopic anisometropia. P < 0.05 was considered to be statistically significant. To adjust for the possible effects of age, sex, refractive errors, and axial length on RNFL thickness, multivariate regression analysis was performed, and a generalized estimating equation 30 was used to account for the correlation between both eyes in individuals. The correlation between RNFL thickness and other continuous variables was determined using Spearman’s rank correlation coefficient (ρ). 
Results
Among 38 patients with unilateral amblyopia, 23 were male and 15 were female. The mean ± SD age was 26.4 ± 18.3 years. The eye with amblyopia was the right eye in 19 patients and the left eye in 19 patients. Best corrected vision of the amblyopic eye ranged from 20/1200 to 20/30. Best corrected vision of the normal eye was equal to or better than 20/20. The mean age of 20 patients with strabismic amblyopia was 27.4 ± 18.6 years, and the mean age of 18 patients with refractive amblyopia was 25.4 ± 18.6 years. The mean age of 17 normal control subjects was 28.5 ± 12.2 years. 
In all 38 patients with unilateral amblyopia, the difference in RNFLT between the amblyopic eyes and the normal fellow eyes was statistically significant (Table 5) . The difference in RNFLTestimated integrals between the amblyopic eyes and the normal fellow eyes was also statistically significant (Table 6) . Multivariate regression analysis with adjustment for axial length, spherical equivalence, age, and sex indicated a significant difference in RNFLT and in RNFLTestimated integrals as well. Although the spherical equivalence in amblyopic eyes (0.17 ± 3.59 D) was higher than that in normal fellow eyes (−0.81 ± 2.33 D), the difference was not statistically significant (P = 0.084). In addition, there was no significant correlation between RNFLT and axial length (ρ = −0.075, P = 0.655) or spherical equivalence (ρ = −0.009, P = 0.956) among all amblyopic eyes. RNFLT in all amblyopic eyes did not correlate with logMAR visual acuity (P = 0.104) after adjustment for age. 
Further analysis was performed separately for strabismic and refractive amblyopia. In the group with strabismic amblyopia, the difference in RNFLT and RNFLTestimated integrals between the amblyopic eyes and the normal fellow eyes did not reach statistical significance. However, in the group of refractive amblyopia, the difference in RNFLT and in RNFLTestimated integrals between the amblyopic eyes and the normal fellow eyes were statistically significant (Tables 5 6)
In the 19 patients with anisometropic amblyopia, the difference between RNFLT and RNFLTestimated integrals in the amblyopic eyes and in the normal fellow eyes both were statistically significant (Tables 5 6) . The differences were significant in the multivariate regression analysis as well. In the control group of 17 patients with nonamblyopic anisometropia, the difference in RNFLT and in RNFLTestimated integrals between the two eyes both did not reach statistical significance (Tables 7 8)
Difference in RNFL thickness may come from glaucomatous damage and subjects older than 40 may confound the data analysis. Therefore, we also analyzed the data excluding subjects older than 40. The number of subjects was reduced to 31 from 38 (amblyopic) and to 13 from 17 (control). With a sample size of 31, the study had more than 80% statistical power to detect a 6% increase in RNFL thickness in amblyopic eyes, compared with the normal eyes. The results of RNFLT and RNFLTestimated integrals of the reduced number also consisted with the results of total number. 
Discussion
During an OCT examination, the selected preset scan radius is automatically modified by the instrument’s software. This modification is assumed to overcome the magnification produced by the patient’s eye. The actual projected scan radius was found to have statistically significant positive correlation with axial length. 29 For each 1-mm increase in axial length, the actual projected scan radius increased approximately 0.06 mm or 3.5%. A final correction should be made by the examiner, by using a control knob, to reach the desired scan radius. This final correction of the actual projected scan radius, already modified by the instrument, should be made, especially in studies investigating the relationship of RNFL thickness measurement with axial length or refractive error. The study also found that theRNFLTestimated integrals area was found to be independent of the scan radius. 29 We did not correct the actual radius when we performed the OCT examination. Therefore, we used two approaches to correct for this. First, we used multivariate regression analysis to adjust the effects of refractive errors and axial length on the measured RNFLT. Second, we used the “retinal nerve fiber layer total area” as a proxy parameter. Our study revealed RNFLT was thicker and RNFLTestimated integrals were larger in the amblyopic eye, especially in refractive amblyopia and in anisometropic amblyopia, but not in strabismic amblyopia. 
The amblyopic process may have an effect on various levels of the visual pathway. Histopathologic changes in the lateral geniculate nucleus and visual cortex have been reported. 
Histologic study of the lateral geniculate nucleus of monkeys with strabismic, anisometropic, and visual deprivation amblyopia reveals marked shrinkage of cells that receive input from the amblyopic eye. 3 4 5 There are similar findings in the lateral geniculate nucleus in human anisometropic amblyopia 6 and strabismic amblyopia. 7  
Wiesel and Hubel 2 8 9 pioneered the application of microelectrode techniques to record directly from single neurons within the visual system of animals to study the effects of normal and abnormal visual experience early in life in visually immature kittens. Extracellular recordings from striate neurons in monkeys with strabismic, anisometropic, and visual deprivation amblyopia and in unilaterally lid-sutured kittens demonstrated a decimation of binocularly driven cells and of cells receiving input from the amblyopic eye. 10 11 12 In humans, positron emission tomography scans revealed a significant reduction of relative cortical blood flow and glucose metabolism during visual stimulation of the amblyopic eye compared with the normal eye. 31  
Retinal involvement in strabismic and/or anisometropic amblyopia is controversial. 13 14 15 16 17 Electroretinograms elicited by patterned stimuli in humans with various types of amblyopia were significantly reduced. 13 The Stiles-Crawford effect or foveal visual pigment density, however, indicated no retinal dysfunction at the level of cone photoreceptors in amblyopic eyes. 14 There have been no studies of either the anatomic or physiologic properties of the retina in monkeys reared with experimental amblyopia due to strabismus or anisometropia. Ikeda and Tremain 15 reported that kittens reared with experimental esotropia had deficits in the spatial resolution of retinal ganglion cells in the area centralis of the deviating eye. Lid suture or surgical strabismus in cats, however, did not result in reduced ganglion cell resolution. 16 17 In the present study, the RNFL thickness measured by OCT was significantly thicker in refractive amblyopia. 
Using a third generation nerve fiber analyzer (GDx; Laser Diagnostic Technologies, San Diego, CA), Colen et al. 32 measured RNFL thickness in strabismic amblyopia, and reported that there was no statistically significant difference between the strabismic amblyopic eyes and normal eyes. In the present study, RNFL thickness was not significantly different between strabismic amblyopic and normal eyes. However, the RNFL was thicker in refractive amblyopic eyes. 
It is unclear why there is a difference in RNFL thickness between amblyopia associated with strabismus versus refractive error. Although strabismic and uncorrected refractive amblyopias are characterized by decreased visual acuity, psychophysical investigations 33 34 35 revealed substantial differences in the visual characteristics of humans with different types of amblyopia. Using a vernier grating stimulus, anisometropic amblyopes show hyperacuity, while strabismic amblyopes show severe losses in vernier acuity. In addition, strabismic amblyopes show “crowding effects” for vernier gratings, while anisometropic amblyopes show no such effects. The findings suggest that different neural losses are associated with amblyopias of different etiologies. In our study, the RNFL was thicker and RNFLTestimated integrals were larger in eyes with refractive amblyopia, suggesting that the process of postnatal reduction of ganglion cells require sharply focused objects as appropriate stimuli. 
In conclusion, in refractive amblyopia, there is a thicker RNFL. This finding requires further histopathologic confirmation. 
 
Table 1.
 
Basic Clinical Data of 20 Patients with Unilateral Amblyopia with Strabismus
Table 1.
 
Basic Clinical Data of 20 Patients with Unilateral Amblyopia with Strabismus
Case Gender Age Amblyopic Eye Squint BCVA Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
A N A N A N
S1 M 12 OD ET 25 PD 20/30 +0.75−5.5×180 −0.25−3.5×180 23.83 23.59 126 116
S2 M 22 OD XT 40 PD 20/200 +4.0−7.0×180 −1.5×180 22.98 23.70 136 128
S3 F 50 OS ET 40 PD 20/600 +7.0−3.5×60 +0.5 21.51 23.75 148 142
S4 F 13 OD ET 40 PD 20/30 +2.75−2.75×180 Plano 22.26 23.07 147 133
S5 M 44 OS XT 25 PD 20/30 +0.25−0.75×180 +1.5−1.5×180 23.90 23.25 137 124
S6 M 12 OD XT 16 PD 20/1200 +0.5−3.5×180 −3.5−0.5×180 24.23 25.77 122 100
S7 F 58 OS ET 16 PD 20/1200 +2.25−0.5×80 +1.75−1.0×125 22.85 22.70 128 121
S8 M 6 OD ET 4 PD 20/200 +6.0 +4.0−1.0×180 19.85 20.04 114 120
S9 F 25 OS XT 10 PD 20/50 +1.5 +0.5 21.27 21.42 146 185
S10 M 74 OS ET, postop. 20/1200 +3.0−1.0×70 +3.25−1.0×50 23.63 23.41 121 133
S11 F 49 OS ET 35 PD 20/1200 +2.25−1.0×150 +1.25−0.5×40 22.15 22.73 118 99
S12 M 15 OS XT 35 PD 20/200 +1.0−1.25×180 −0.5 22.25 25.84 115 108
S13 M 20 OD ET 10 PD 20/200 +0.25 −0.25 23.52 23.63 123 135
S14 F 23 OS XT 90 PD 20/200 +3.25−1.5×180 −1.5−1.25×180 21.83 24.11 132 92
S15 F 20 OS XT 30 PD 20/200 Plano Plano 23.16 23.17 160 162
S16 M 10 OD ET 40 PD 20/30 −0.25 Plano 24.08 23.01 126 128
S17 F 12 OD XT 18 PD 20/100 −6.0−1.0×180 Plano 25.28 23.06 133 141
S18 M 20 OD XT 12 PD 20/60 −6.0−7.5×180 3.0×180 26.07 24.20 122 123
S19 F 24 OS XT 25 PD 20/200 −1.0−2.25×80 −9.5−1.0×10 23.81 28.06 128 129
S20 M 38 OD XT 45 PD 20/60 −4.0−1.0×80 −3.0−1.0×120 26.26 25.02 147 146
Table 2.
 
Basic Clinical Data of 18 Patients with Refractive Amblyopia without Strabismus
Table 2.
 
Basic Clinical Data of 18 Patients with Refractive Amblyopia without Strabismus
Case Gender Age Amblyopic Eye BCVA Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
A N A N A N
R1 M 9 OD 20/40 +1.5−0.5×180 −0.75 20.05 23.99 150 130
R2 M 20 OS 20/100 +1.5−1.75×180 Plano 23.39 23.75 126 127
R3 M 9 OD 20/30 +4.0−0.5×160 Plano 22.14 23.06 154 130
R4 M 75 OD 20/60 +3.0−4.75×110 Plano 23.60 23.56 116 101
R5 M 18 OS 20/100 +3.75−0.75×180 +0.5−0.5×90 22.32 23.00 136 132
R6 M 71 OD 20/200 +4.75−1.5×90 +2.75−1.25×90 22.51 22.36 112 94
R7 M 23 OD 20/100 +0.5 −4.5−0.5×180 24.68 27.19 137 135
R8 F 22 OS 20/100 +4.0−0.5×180 −0.5−0.5×180 22.21 25.13 157 134
R9 M 28 OS 20/600 +5.0−1.5×35 −0.5×90 22.47 24.08 122 102
R10 F 20 OS 20/100 +2.0−1.0×180 −1.75−1.5×180 23.04 24.27 180 151
R11 F 21 OD 20/50 +1.5−0.75×90 −0.25 24.05 23.90 161 133
R12 F 8 OS 20/200 +2.5−0.75×180 +0.25−0.5×90 21.80 23.00 128 112
R13 F 33 OD 20/50 +5.25−1.5×160 +0.5−1.0×180 20.30 22.04 161 145
R14 M 25 OS 20/30 −2.0−2.0×180 −4.25−0.5×155 24.79 25.98 142 142
R15 M 10 OD 20/60 −4.25−1.0×40 −1.25 24.53 23.65 153 133
R16 M 24 OS 20/40 −5.25 −1.75 25.78 24.71 121 119
R17 M 20 OD 20/50 −0.25−4.0×50 −1.75−0.75×180 24.65 24.42 157 163
R18 F 21 OS 20/300 −6.0−2.5×60 Plano 25.60 23.18 147 152
Table 3.
 
Basic Clinical Data of 19 Patients with Amblyopia with Anisometropia
Table 3.
 
Basic Clinical Data of 19 Patients with Amblyopia with Anisometropia
Case Gender Age Amblyopic Eye Squint BCVA Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
A N A N A N
S3 F 50 OS ET 40 PD 20/600 +7.0−3.5×60 +0.5 21.51 23.75 148 142
S6 M 12 OD XT 16 PD 20/1200 +0.5−3.5×180 −3.5−0.5×180 24.23 25.77 122 100
S8 M 6 OD ET 4 PD 20/200 +6.0 +4.0−1.0×180 19.85 20.04 114 120
S14 F 23 OS XT 90 PD 20/200 +3.25−1.5×180 −1.5−1.25×180 21.83 24.11 132 92
S17 F 12 OD XT 18 PD 20/100 −6.0−1.0×180 Plano 25.28 23.06 133 141
S18 M 20 OD XT 12 PD 20/60 −6.0−7.5×180 −3.0×180 26.07 24.20 122 123
S19 F 24 OS XT 25 PD 20/200 −1.0−2.25×80 −9.5−1.0×10 23.81 28.06 128 129
R1 M 9 OD ortho 20/40 +1.5−0.5×180 −0.75 20.05 23.99 150 130
R3 M 9 OD ortho 20/30 +4.0−0.5×160 Plano 22.14 23.06 154 130
R5 M 18 OS ortho 20/100 +3.75−0.75×180 +0.5−0.5×90 22.32 23.00 136 132
R7 M 23 OD ortho 20/100 +0.5 −4.5−0.5×180 24.68 27.19 137 135
R8 F 22 OS ortho 20/100 +4.0−0.5×180 −0.5−0.5×180 22.21 25.13 157 134
R9 M 28 OS ortho 20/600 +5.0−1.5×35 −0.5×90 22.47 24.08 122 102
R10 F 20 OS ortho 20/100 +2.0−1.0×180 −1.75−1.5×180 23.04 24.27 180 151
R12 F 8 OS ortho 20/200 +2.5−0.75×180 +0.25−0.5×90 21.80 23.00 128 112
R13 F 33 OD ortho 20/50 +5.25−1.5×160 +0.5−1.0×180 20.30 22.04 161 145
R15 M 10 OD ortho 20/60 −4.25−1.0×40 −1.25 24.53 23.65 153 133
R16 M 24 OS ortho 20/40 −5.25 −1.75 25.78 24.71 121 119
R18 F 21 OS ortho 20/300 −6.0−2.5×60 Plano 25.60 23.18 147 152
Table 4.
 
Basic Clinical Data of 17 Patients with Nonamblyopic Anisometropia
Table 4.
 
Basic Clinical Data of 17 Patients with Nonamblyopic Anisometropia
Case Gender Age More Myopic Eye Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
More Less More Less More Less
C1 F 26 OS −8.75−0.5×135 −5.5−1.0×60 25.50 24.46 132 132
C2 F 22 OS −7.75−1.5×180 −3.5−2.5×180 26.24 24.20 121 105
C3 M 53 OS −5.5 −2.0−2.0×180 26.97 25.99 99 104
C4 F 22 OS −5.25−0.75×50 +1.25−2.0×180 25.08 23.14 144 145
C5 M 35 OD −5.25−0.5×180 −1.75−1.0×180 26.60 25.10 120 128
C6 F 14 OS −5.0 −1.0 25.10 23.48 155 150
C7 F 20 OD −5.0 −1.5 25.06 23.56 85 87
C8 F 27 OD −4.75 −0.25−1.0×180 24.81 23.04 124 123
C9 F 14 OD −4.5−2.0×180 −2.25−2.5×180 24.88 24.34 133 135
C10 M 26 OD −4.5 −0.5 24.94 23.51 99 105
C11 M 41 OD −4.25−0.5×90 −1.0−0.5×130 23.54 22.51 110 124
C12 F 14 OD −3.5 +1.5−0.75×180 25.44 23.00 117 117
C13 F 43 OS −3.0 −0.75 24.83 24.20 130 135
C14 M 12 OS −2.0 Plano 23.31 22.76 154 142
C15 F 38 OD −2.0 Plano 24.60 24.57 102 91
C16 M 35 OD −1.75−0.75×180 Plano 24.00 23.86 141 141
C17 F 42 OS −0.75−1.75×180 Plano 23.07 22.32 101 97
Figure 1.
 
A single OCT scan of a normal eye.
Figure 1.
 
A single OCT scan of a normal eye.
Table 5.
 
Comparison of RNFL Thickness in Amblyopic and Normal Eyes
Table 5.
 
Comparison of RNFL Thickness in Amblyopic and Normal Eyes
Mean ± SD (μm) Spherical Equivalence (D) Axial Length (mm) Paired-t Test (P) Adjusted P
Amblyopic Normal Amblyopic Normal Amblyopic Normal
Total patients (n = 38) 136.6 ± 16.5 128.9 ± 19.9 0.17 ± 3.59 −0.81 ± 2.33 23.40 ± 1.53 23.85 ± 1.46 0.003 0.006
Amblyopia with strabismus (n = 20) 131.5 ± 12.6 128.3 ± 21.5 −0.13 ± 3.6 −0.71 ± 2.82 23.39 ± 1.63 23.73 ± 1.66 0.085 0.500
Refractive amblyopia without strabismus (n = 18) 142.2 ± 18.6 129.7 ± 18.5 0.49 ± 3.57 −0.92 ± 1.70 23.41 ± 1.46 24.00 ± 1.23 <0.001 <0.001
Amblyopia with anisometropia (n = 19) 139.2 ± 17.2 127.5 ± 16.8 0.10 ± 4.73 −1.32 ± 1.83 23.18 ± 1.83 24.04 ± 1.75 0.001 <0.001
Table 6.
 
Comparison of RNFLTestimated integrals in Amblyopic and Normal Eyes
Table 6.
 
Comparison of RNFLTestimated integrals in Amblyopic and Normal Eyes
Amblyopic Normal Paired-t Test (P) Adjusted P
Total patients (n = 38) 1,386,052 ± 199,609 1,326,627 ± 216,605 <0.001 0.006
Amblyopia with strabismus (n = 20) 1,359,696 ± 152,690 1,337,361 ± 215,409 0.507 0.500
Refractive amblyopia without strabismus (n = 18) 1,470,697 ± 207,649 1,376,891 ± 224,683 0.005 <0.001
Amblyopia with anisometropia (n = 19) 1,432,455 ± 188,711 1,342,034 ± 190,211 0.003 <0.001
Table 7.
 
Comparison of RNFL Thickness Between Eyes in Nonamblyopic Anisometropia
Table 7.
 
Comparison of RNFL Thickness Between Eyes in Nonamblyopic Anisometropia
Mean ± SD (μm) Spherical Equivalence (D) Axial Length (mm) Paired-t Test (P) Adjusted P
More Myopia Less Myopia More Myopia Less Myopia More Myopia Less Myopia
Nonamblyopia with anisometropia (n = 17) 121.5 ± 20.4 121.2 ± 19.8 −4.51 ± 2.14 −1.41 ± 1.93 24.94 ± 1.07 23.76 ± 0.96 0.875 0.922
Table 8.
 
Comparison of RNFLTestimated integrals between Eyes in Nonamblyopic Anisometropia
Table 8.
 
Comparison of RNFLTestimated integrals between Eyes in Nonamblyopic Anisometropia
More Myopia Less Myopia Paired-t Test (P) Adjusted P
Nonamblyopia with anisometropia(n = 17) 1,327,434 ± 219,986 1,260,778 ± 204,979 0.009 0.847
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Figure 1.
 
A single OCT scan of a normal eye.
Figure 1.
 
A single OCT scan of a normal eye.
Table 1.
 
Basic Clinical Data of 20 Patients with Unilateral Amblyopia with Strabismus
Table 1.
 
Basic Clinical Data of 20 Patients with Unilateral Amblyopia with Strabismus
Case Gender Age Amblyopic Eye Squint BCVA Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
A N A N A N
S1 M 12 OD ET 25 PD 20/30 +0.75−5.5×180 −0.25−3.5×180 23.83 23.59 126 116
S2 M 22 OD XT 40 PD 20/200 +4.0−7.0×180 −1.5×180 22.98 23.70 136 128
S3 F 50 OS ET 40 PD 20/600 +7.0−3.5×60 +0.5 21.51 23.75 148 142
S4 F 13 OD ET 40 PD 20/30 +2.75−2.75×180 Plano 22.26 23.07 147 133
S5 M 44 OS XT 25 PD 20/30 +0.25−0.75×180 +1.5−1.5×180 23.90 23.25 137 124
S6 M 12 OD XT 16 PD 20/1200 +0.5−3.5×180 −3.5−0.5×180 24.23 25.77 122 100
S7 F 58 OS ET 16 PD 20/1200 +2.25−0.5×80 +1.75−1.0×125 22.85 22.70 128 121
S8 M 6 OD ET 4 PD 20/200 +6.0 +4.0−1.0×180 19.85 20.04 114 120
S9 F 25 OS XT 10 PD 20/50 +1.5 +0.5 21.27 21.42 146 185
S10 M 74 OS ET, postop. 20/1200 +3.0−1.0×70 +3.25−1.0×50 23.63 23.41 121 133
S11 F 49 OS ET 35 PD 20/1200 +2.25−1.0×150 +1.25−0.5×40 22.15 22.73 118 99
S12 M 15 OS XT 35 PD 20/200 +1.0−1.25×180 −0.5 22.25 25.84 115 108
S13 M 20 OD ET 10 PD 20/200 +0.25 −0.25 23.52 23.63 123 135
S14 F 23 OS XT 90 PD 20/200 +3.25−1.5×180 −1.5−1.25×180 21.83 24.11 132 92
S15 F 20 OS XT 30 PD 20/200 Plano Plano 23.16 23.17 160 162
S16 M 10 OD ET 40 PD 20/30 −0.25 Plano 24.08 23.01 126 128
S17 F 12 OD XT 18 PD 20/100 −6.0−1.0×180 Plano 25.28 23.06 133 141
S18 M 20 OD XT 12 PD 20/60 −6.0−7.5×180 3.0×180 26.07 24.20 122 123
S19 F 24 OS XT 25 PD 20/200 −1.0−2.25×80 −9.5−1.0×10 23.81 28.06 128 129
S20 M 38 OD XT 45 PD 20/60 −4.0−1.0×80 −3.0−1.0×120 26.26 25.02 147 146
Table 2.
 
Basic Clinical Data of 18 Patients with Refractive Amblyopia without Strabismus
Table 2.
 
Basic Clinical Data of 18 Patients with Refractive Amblyopia without Strabismus
Case Gender Age Amblyopic Eye BCVA Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
A N A N A N
R1 M 9 OD 20/40 +1.5−0.5×180 −0.75 20.05 23.99 150 130
R2 M 20 OS 20/100 +1.5−1.75×180 Plano 23.39 23.75 126 127
R3 M 9 OD 20/30 +4.0−0.5×160 Plano 22.14 23.06 154 130
R4 M 75 OD 20/60 +3.0−4.75×110 Plano 23.60 23.56 116 101
R5 M 18 OS 20/100 +3.75−0.75×180 +0.5−0.5×90 22.32 23.00 136 132
R6 M 71 OD 20/200 +4.75−1.5×90 +2.75−1.25×90 22.51 22.36 112 94
R7 M 23 OD 20/100 +0.5 −4.5−0.5×180 24.68 27.19 137 135
R8 F 22 OS 20/100 +4.0−0.5×180 −0.5−0.5×180 22.21 25.13 157 134
R9 M 28 OS 20/600 +5.0−1.5×35 −0.5×90 22.47 24.08 122 102
R10 F 20 OS 20/100 +2.0−1.0×180 −1.75−1.5×180 23.04 24.27 180 151
R11 F 21 OD 20/50 +1.5−0.75×90 −0.25 24.05 23.90 161 133
R12 F 8 OS 20/200 +2.5−0.75×180 +0.25−0.5×90 21.80 23.00 128 112
R13 F 33 OD 20/50 +5.25−1.5×160 +0.5−1.0×180 20.30 22.04 161 145
R14 M 25 OS 20/30 −2.0−2.0×180 −4.25−0.5×155 24.79 25.98 142 142
R15 M 10 OD 20/60 −4.25−1.0×40 −1.25 24.53 23.65 153 133
R16 M 24 OS 20/40 −5.25 −1.75 25.78 24.71 121 119
R17 M 20 OD 20/50 −0.25−4.0×50 −1.75−0.75×180 24.65 24.42 157 163
R18 F 21 OS 20/300 −6.0−2.5×60 Plano 25.60 23.18 147 152
Table 3.
 
Basic Clinical Data of 19 Patients with Amblyopia with Anisometropia
Table 3.
 
Basic Clinical Data of 19 Patients with Amblyopia with Anisometropia
Case Gender Age Amblyopic Eye Squint BCVA Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
A N A N A N
S3 F 50 OS ET 40 PD 20/600 +7.0−3.5×60 +0.5 21.51 23.75 148 142
S6 M 12 OD XT 16 PD 20/1200 +0.5−3.5×180 −3.5−0.5×180 24.23 25.77 122 100
S8 M 6 OD ET 4 PD 20/200 +6.0 +4.0−1.0×180 19.85 20.04 114 120
S14 F 23 OS XT 90 PD 20/200 +3.25−1.5×180 −1.5−1.25×180 21.83 24.11 132 92
S17 F 12 OD XT 18 PD 20/100 −6.0−1.0×180 Plano 25.28 23.06 133 141
S18 M 20 OD XT 12 PD 20/60 −6.0−7.5×180 −3.0×180 26.07 24.20 122 123
S19 F 24 OS XT 25 PD 20/200 −1.0−2.25×80 −9.5−1.0×10 23.81 28.06 128 129
R1 M 9 OD ortho 20/40 +1.5−0.5×180 −0.75 20.05 23.99 150 130
R3 M 9 OD ortho 20/30 +4.0−0.5×160 Plano 22.14 23.06 154 130
R5 M 18 OS ortho 20/100 +3.75−0.75×180 +0.5−0.5×90 22.32 23.00 136 132
R7 M 23 OD ortho 20/100 +0.5 −4.5−0.5×180 24.68 27.19 137 135
R8 F 22 OS ortho 20/100 +4.0−0.5×180 −0.5−0.5×180 22.21 25.13 157 134
R9 M 28 OS ortho 20/600 +5.0−1.5×35 −0.5×90 22.47 24.08 122 102
R10 F 20 OS ortho 20/100 +2.0−1.0×180 −1.75−1.5×180 23.04 24.27 180 151
R12 F 8 OS ortho 20/200 +2.5−0.75×180 +0.25−0.5×90 21.80 23.00 128 112
R13 F 33 OD ortho 20/50 +5.25−1.5×160 +0.5−1.0×180 20.30 22.04 161 145
R15 M 10 OD ortho 20/60 −4.25−1.0×40 −1.25 24.53 23.65 153 133
R16 M 24 OS ortho 20/40 −5.25 −1.75 25.78 24.71 121 119
R18 F 21 OS ortho 20/300 −6.0−2.5×60 Plano 25.60 23.18 147 152
Table 4.
 
Basic Clinical Data of 17 Patients with Nonamblyopic Anisometropia
Table 4.
 
Basic Clinical Data of 17 Patients with Nonamblyopic Anisometropia
Case Gender Age More Myopic Eye Refractive Error (D) Axial Length (mm) Average RNFLT (μm)
More Less More Less More Less
C1 F 26 OS −8.75−0.5×135 −5.5−1.0×60 25.50 24.46 132 132
C2 F 22 OS −7.75−1.5×180 −3.5−2.5×180 26.24 24.20 121 105
C3 M 53 OS −5.5 −2.0−2.0×180 26.97 25.99 99 104
C4 F 22 OS −5.25−0.75×50 +1.25−2.0×180 25.08 23.14 144 145
C5 M 35 OD −5.25−0.5×180 −1.75−1.0×180 26.60 25.10 120 128
C6 F 14 OS −5.0 −1.0 25.10 23.48 155 150
C7 F 20 OD −5.0 −1.5 25.06 23.56 85 87
C8 F 27 OD −4.75 −0.25−1.0×180 24.81 23.04 124 123
C9 F 14 OD −4.5−2.0×180 −2.25−2.5×180 24.88 24.34 133 135
C10 M 26 OD −4.5 −0.5 24.94 23.51 99 105
C11 M 41 OD −4.25−0.5×90 −1.0−0.5×130 23.54 22.51 110 124
C12 F 14 OD −3.5 +1.5−0.75×180 25.44 23.00 117 117
C13 F 43 OS −3.0 −0.75 24.83 24.20 130 135
C14 M 12 OS −2.0 Plano 23.31 22.76 154 142
C15 F 38 OD −2.0 Plano 24.60 24.57 102 91
C16 M 35 OD −1.75−0.75×180 Plano 24.00 23.86 141 141
C17 F 42 OS −0.75−1.75×180 Plano 23.07 22.32 101 97
Table 5.
 
Comparison of RNFL Thickness in Amblyopic and Normal Eyes
Table 5.
 
Comparison of RNFL Thickness in Amblyopic and Normal Eyes
Mean ± SD (μm) Spherical Equivalence (D) Axial Length (mm) Paired-t Test (P) Adjusted P
Amblyopic Normal Amblyopic Normal Amblyopic Normal
Total patients (n = 38) 136.6 ± 16.5 128.9 ± 19.9 0.17 ± 3.59 −0.81 ± 2.33 23.40 ± 1.53 23.85 ± 1.46 0.003 0.006
Amblyopia with strabismus (n = 20) 131.5 ± 12.6 128.3 ± 21.5 −0.13 ± 3.6 −0.71 ± 2.82 23.39 ± 1.63 23.73 ± 1.66 0.085 0.500
Refractive amblyopia without strabismus (n = 18) 142.2 ± 18.6 129.7 ± 18.5 0.49 ± 3.57 −0.92 ± 1.70 23.41 ± 1.46 24.00 ± 1.23 <0.001 <0.001
Amblyopia with anisometropia (n = 19) 139.2 ± 17.2 127.5 ± 16.8 0.10 ± 4.73 −1.32 ± 1.83 23.18 ± 1.83 24.04 ± 1.75 0.001 <0.001
Table 6.
 
Comparison of RNFLTestimated integrals in Amblyopic and Normal Eyes
Table 6.
 
Comparison of RNFLTestimated integrals in Amblyopic and Normal Eyes
Amblyopic Normal Paired-t Test (P) Adjusted P
Total patients (n = 38) 1,386,052 ± 199,609 1,326,627 ± 216,605 <0.001 0.006
Amblyopia with strabismus (n = 20) 1,359,696 ± 152,690 1,337,361 ± 215,409 0.507 0.500
Refractive amblyopia without strabismus (n = 18) 1,470,697 ± 207,649 1,376,891 ± 224,683 0.005 <0.001
Amblyopia with anisometropia (n = 19) 1,432,455 ± 188,711 1,342,034 ± 190,211 0.003 <0.001
Table 7.
 
Comparison of RNFL Thickness Between Eyes in Nonamblyopic Anisometropia
Table 7.
 
Comparison of RNFL Thickness Between Eyes in Nonamblyopic Anisometropia
Mean ± SD (μm) Spherical Equivalence (D) Axial Length (mm) Paired-t Test (P) Adjusted P
More Myopia Less Myopia More Myopia Less Myopia More Myopia Less Myopia
Nonamblyopia with anisometropia (n = 17) 121.5 ± 20.4 121.2 ± 19.8 −4.51 ± 2.14 −1.41 ± 1.93 24.94 ± 1.07 23.76 ± 0.96 0.875 0.922
Table 8.
 
Comparison of RNFLTestimated integrals between Eyes in Nonamblyopic Anisometropia
Table 8.
 
Comparison of RNFLTestimated integrals between Eyes in Nonamblyopic Anisometropia
More Myopia Less Myopia Paired-t Test (P) Adjusted P
Nonamblyopia with anisometropia(n = 17) 1,327,434 ± 219,986 1,260,778 ± 204,979 0.009 0.847
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